The present invention relates to refractory compositions capable, when mixed with water, of forming hydraulic-setting castable refractories for lining metallurgical vessels used to process metals containing large amounts of aluminum.
It is well known that lined vessels such as aluminum melting furnaces are subject to attack by the aluminum, often resulting in penetration by the aluminum into the lining, adhesion of the aluminum to the lining, and other corrosive effects of the aluminum on the lining.
Efforts to overcome this problem are described, for example, in U.S. Pat. Nos. 4,088,502 and 4,158,568, wherein amounts of a zinc borosilicate frit are added in an effort to prevent such corrosion. However, addition of such zinc borosilicates, while generally resulting in preventing penetration of aluminum into the lining, does not eliminate the problem of adhesion of the aluminum to the lining, making it difficult to separate the aluminum from the vessel and greatly decrease the load-bearing properties of the lining.
Others such as in U.S. Pat. No. 4,126,474 have added barium sulfate to the refractory in an effort to overcome these problems but it not only does not eliminate adherence of the metal to the refractory, but also tends to lower the load-bearing properties of the refractory.
Efforts to increase the strength of the castable are described in the prior art as in U.S. Pat. No. 4,348,236, which uses lower levels of the borosilicate frit in preparation of the castable, but here again there is strong adherence of the metal to the refractory.